1. Field of the Invention
This invention is directed to the field of centrifuges, to seals therefor, and to bowls for centrifuges. Certain embodiments are particularly suited to applications in the field of blood-processing.
2. Description of the Prior Art
In maintaining or handling blood it is often necessary to perform certain processes, including centrifuging. Among the prior art devices made to meet the stringent requirements of handling blood are the centrifuges of U.S. Pat. No. 3,145,713 and U.S. Pat. No. 3,317,127. The centrifuges described in these patents have applications to pumps, centrifuges, and mixing devices in general. In such centrifuges for sterile processing it is necessary to effectively seal the area between the rotating and stationary members of the device.
In centrifuges for handling fluids subject to contamination, the centrifuge bowl should rotate, but the flow lines for the fluid inlet and outlet should remain stationary. This requires a rotating seal which is effective when frictional heating is so low and the dissipation of heat is so high that the blood, or other heat sensitive fluid, is not exposed to high temperatures. The seal should not produce abraded particulate contaminants which might flow into the blood or other liquid and it is desirable that the seals be easy to install and easy to sterilize. Also the seal should achieve high reliability in service and be capable of tolerating misalignment and vibration.
U.S. Pat. Nos. 3,409,213 and 3,565,330 present examples of rotary centrifuge seals. These patents teach rotary seals which are formed from a stationary rigid low friction member in contact with a moving rigid member to create a dynamic seal, and an elastomeric member which provides a resilient static seal as well as a closing force between the surfaces of the dynamic seal. Another rotary seal, described in U.S. Pat. No. 3,801,142 has a pair of seal elements having confronting annular fluid-tight sealing surfaces which are maintained in a rotatable, but fluid-tight, relationship.
Another rotary seal used in a blood-processing centrifuge known as the "B. T. Bowl", marketed by Bellco, Mirandola, Italy, has a ceramic ring attached to rotatable elements of the centrifuge and a fixed graphite ring attached to stationary centrifuge elements, the ring members being in sealing relationship with each other. An elastomeric diaphragm is connected at one end to an adapter ring for the graphite ring and at the other end to a stationary part of the centrifuge. This type of rotary seal lacks adequate provision for assuring that wear particles will be ingested and expelled to the outside without entry into the fluid pathway.
Because of the outwardly tapering wall shape of the rotating bowl in various prior art centrifuging devices, forces are created which impel the bowl upward. If the apparatus holding the bowl in place fails, comes loose, or is improperly connected, these upward forces can cause the bowl to disengage resulting in damage to the device and possible injury to persons nearby. Also, because of the relatively sharp slope of the bowl walls, the forces which act on the liquid are not uniform or nearly uniform.